1. Field of the Invention
The present invention relates to a coal liquefaction process and an apparatus therefor, and more particularly to a coal liquefaction process which can be performed efficiently to improve the yield of reaction products, particularly, the heavy oil product which is well suited as a metallurgical carbonaceous carbon material.
2. Description of the Prior Art
A coal liquefaction process is known in which coal fines are treated in the presence of hydrogen to liquify the coal. The coal fines used in the coal liquefaction process include low grade coals such as bituminous, semi-bituminous, and sub-bituminous coals and lignite as well as similar solid carbonaceous materials such as shale. According to the conventional process of the type described, coal fines, a hydrocarbon solvent having a boiling point of over 150.degree. C., and a suitable catalyst such as a ferro-sulfuric system catalyst, if desired, are mixed in a slurry, (The use of a catalyst may not be necessary or essential because the ash in coal functions as a catalyst), and then the slurry is preheated in a preheater. A high pressure hydrogen-rich gas is added thereto preferably prior to the preheating of the slurry. The preheated slurry and a high pressure hydrogen-rich gas are passed into a reactor where a hydrogenation reaction is conducted at a high temperature and pressure, e.g., 300.degree. to 500.degree. C., 50 to 700 atms. Then, a mixture of reaction products of reactor effluent is introduced into two or more separators connected through pressure-reducing valves to each other, wherein the pressure is progressively reduced and gas, liquid and solid are flash distilled.
At the present time, the objective in the liquefaction of coal is to form a heavy oil product having a high boiling point for use as a metallurgical carbonaceous material for use, for instance, in the manufacture of steel-making coke or carbon electrodes for alumina electrolysis. The liquid product or effluent, generally, includes solids such as ash, unreacted coal, catalysts, and insoluble reaction products. Accordingly, the removal of these elements would improve the quality of the heavy oil product for its intended use. In general, a metallurgical carbonaceous material should have an ash content of less than 10%.
Coal liquefaction process hitherto has been beset with many formidable problems, which will be described as follows: